Soluble phenolic compounds of perennial ryegrass (Lolium perenne L.): Potential effects on animal performance, and challenges in determining profiles and concentrations

Abstract

Perennial ryegrass (Lolium perenne L.) contains phenolic compounds esterified to cell walls, and it also contains soluble phenolic compounds in the vacuole. Soluble phenolic compounds of perennial ryegrass may be important to the performance of grazing animals, due to their roles as substrates for polyphenol oxidase and as antioxidants. However, the soluble phenolic compound profile of perennial ryegrass has not been completely identified, making it difficult to determine which compounds could be important for animal performance. This review summarizes information on perennial ryegrass phenolic compound composition and concentration. Chlorogenic acid and its isomers have been characterized in many varieties of perennial ryegrass, as has thesinine rhamnoside. Many glycosides of various flavonoids have been reported, but the glycosidic moieties have not been completely characterized. Condensed tannins have been found in seeds, but their presence in leaf tissue has been variable. Concentration and composition of soluble phenolic compounds of perennial ryegrass are affected by sample preparation, presence of pathogens or endophytes, environmental stresses, time of day, plant maturity, and genetic background. The challenges in characterizing the soluble phenolic compounds of perennial ryegrass lie in the difficulties of comparing results across studies, due to the abovementioned sources of variation, and in the need for consistent extraction methods, separation methods, and adequate amounts of material.